A new chloroplast thylakoid gene, pdf1, is linked to Lct1

If the proteins of the maize chloroplast thylakoid are run out on a density-gradient Laemmli SDS urea polyacrylamide gel, there is between the 21.5 Kd and 31 Kd markers a cluster of at least six major proteins (and several more minor bands). Under certain gel conditions (full details upon request from the author) there is a well separated pair of pink-hued (Coomassie Blue-stained) bands which are the fastest migrating proteins of that cluster. An allele derived from Zea luxurians causes the faster of this pink pair to migrate still faster (farther on the gel). Z. diploperennis and Z. perennis mimic the phenotype of Z. luxurians. This phenotype of luxurians is constant in accessions from Guatemala, Honduras and Florida. Plants of the generation M. d. x Z. m.) x Z. m.) x Z. m. are segregating this phenotype. Chalco, Nobogame, Huehuetenango Balsas, and all maizes (Corn Belt and exotic) have the slower migrating phenotype.

No F2 data are in hand to test the mode of inheritance. However, a dominant-recessive relationship is suggested by absence of apparent band broadening on the gel. The following data for crosses involving Z. luxurians are presented:


I designate this nuclear factor pdf1 (pink doublet, faster band). There are two alleles: pdf1-Zm, the recessive factor common in domesticated maize; and Pdf1-Zl, the dominant allele derived from Z. luxurians. I do not now designate the genotype of diploperennis, though the test for allelism is partially set up. I am advancing this factor into several standard maize lines.

The data gathered suggest a linkage relationship with Lct1 (see details of Lct1 alleles in the main Columbia, MO section). The data are:


It is clear from the data that these two loci can not be locked in a "supergene" block by a small local inversion.

Others are welcome to work with these genes. A small quantity of seed for increase is available upon request.

Stephen A. Modena

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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